1. Field of the Invention
The present invention relates to an HARQ method in a P2P communication system and an apparatus using the same.
2. Related Art
P2P Communication
In a mobile communication system, a transmitting terminal communicates with a receiving terminal always through a mobile communication network irrespective of a distance between the transmitting terminal and the receiving terminal so as to perform communication with other terminals. In other words, a connection with the receiving terminal is established via a base station and a switching station that constitutes a mobile communication system regardless of the distance between the transmitting terminal and the receiving terminal. However, in case the transmitting terminal is very close to the receiving terminal, it may be more reasonable to fulfill a direct communication between the two terminals without going through a base station. Here, the inter-terminal direct communication not passing through a base station is hereinafter referred to as peer-to-peer (“P2P”) communication. Various services may be provided through the P2P communication, such as transmission of mass files, VoIP, and video conferencing, and the same quality of service as the existing service that is provided through a base station may be achieved.
HARQ (Hybrid Automatic Repeat Request)
A technology for raising reliability of wireless communication is automatic repeat request (ARQ). In the ARQ, if a receiver fails to receive a data signal, a transmitter resends a data signal. Further, another technology is hybrid automatic repeat request (HARQ) that combines forward error correction (FEC) with ARQ. A receiver using HARQ basically attempts error correction on a received data signal and determines whether to resend using an error detection code. The error detection may use Cyclic redundancy check (CRC). If no error is detected from the data signal through a CRC detection process, the receiver determines that the data signal has been successfully decoded. In such case, the receiver sends an acknowledgement (ACK) signal to the transmitter. If an error is detected from the data signal through the CRC detection process, the receiver determines that decoding of the data signal has failed. In such case, the receiver sends a not-acknowledgement (NACK) signal to the transmitter. When receiving the NACK signal, the transmitter may resend the data signal to the receiver.
As such, HARQ is an important technology for increasing the reliability of wireless communication. However, in performing HARQ, when a data signal is transmitted or received and when an HARQ ACK/NACK signal is transmitted or received for the data signal matter. Accordingly, a need exists for a method of efficiently performing HARQ in a wireless communication system.